This invention relates to snap action magnetic circuit breakers. More particularly, the invention relates to improved circuit breaker mechanisms for use in compact snap action breakers combining the functions of switches and circuit breakers.
Compact snap action circuit breakers are disclosed in commonly assigned U.S. Pat. No. 3,806,848 issued Apr. 23, 1974 to George S. Harper et al. (the '806 patent) and U.S. Pat. No. 4,117,285 issued Sept. 26, 1978 to George S. Harper (the '285 patent). In the devices described in the '806 and '285 patents, a toggle mechanism is tripped by the attraction of an armature to an electromagnet when the current through the electromagnet coil exceeds a predetermined value.
A movable contact of the circuit breaker is coupled to an overcenter spring so that upon tripping, the contacts open with a positive snap action to minimize contact arcing. The overcenter spring also acts on the movable contact when the circuit breaker contacts are open or closed manually. This snap action opening and closing of the circuit breaker contacts during manual operation has the advantage that it makes it impossible for the contacts to be "teased" in such a way as to damage the circuit breaker.
The handle mechanisms described in the '848 and '285 patent are of the toggle, rocker-arm, or push-push (push on-push off) type. While these handle mechanisms are appropriate for certain types of operations, other operations require a push-pull switch handle mechanism. Still other operations require a mechanism which can be manually operated to set the breaker in its contact closed position but prevents manual opening of the breaker contacts.
Snap action circuit breakers of the type to which this invention is directed are frequently incorporated into control panels or like structures in which numerous breakers are mounted in banks aligned in rows and columns. For example, computer manufacturers will often incorporate a circuit breaker into each separate power supply line to prevent electrical problems in one section of the computer from spilling over and affecting other sections. Often in large scale computer installations, fifty to one hundred or more circuit breakers may be utilized. Normally, the circuit breakers will be located in one cabinet in banks. It is desirable to provide a quick visual means for determining which breaker(s) among the fifty to one hundred or more located in a cabinet has tripped due to an electrical overload. The push-pull type of breaker handle mechanism of the present invention provides such a quick means for visually isolating the tripped breaker without requiring the use of additional electrical circuits using bulb type indicators which can burn out but which also maintain the manual opening capability of the breaker assembly.
Other types of installation require a breaker mechanism which cannot be manually tripped open. In the medical electronics field, for example, it is desirable to use circuit breakers in sophisticated electronic monitoring and/or life support equipment. It will be apparent that, in the operation of such equipment, the inadvertant manual opening of circuit-breakers could have severe adverse or disasterous consequences. It is therefore desirable to provide a switch-breaker mechanism which cannot be inadvertantly manually tripped. It is also desirable to provide a breaker mechanism having the same quick visual contacts open recognition feature described above. In one embodiment, this invention provides such a breaker.
The present invention, described with respect to the appended drawing and the detailed description of the preferred embodiments below, provides new and improved handle mechanisms consistent with the aforedescribed operating requirements. Specifically, one embodiment of this invention provides a push to close breaker setting mechanism which cannot be manually triggered into the contacts open position; a second embodiment of the invention provides a push to close, pull to open operating mechanism having the features of a push-pull manually operated switch with the overcurrent protection action of a circuit breaker. Other features and advantages of this invention will be apparent from the following description of the preferred embodiments.